Field of the Invention
This invention relates to an improvement in a cooling water circulating structure capable of improving the cooling performance of an oil cooler, reducing the number of pipes around an engine body, simplifying the arrangement of parts around an engine and miniaturizing the engine by improving a circulating path for engine cooling water.
The miniaturization and the reduction of weight of an engine for automobiles are progressing, and it has strongly been demanded that not only an engine body but also pipes provided outside the engine body be simplified and omitted to as great an extent as possible with a view to saving the space and lightening the engine. As a part of the measures for dealing with these problems, the improving of the cooling water circulating passages accounting for almost all the pipes provided outside the engine is also being promoted.
The cooling water circulating structure for engines will now be described. The cooling water discharged from a cooling water pump is supplied to a cylinder block and a cylinder head and cools an engine body. This cooling water is then circulated to a suction port of the cooling water pump via, for example, four paths, which will be described later, i.e. (a) a passage for a radiator, (b) a passage for a heater core, (c) a passage for an oil cooler, and (d) a bypass passage.
The (a) passage for the radiator is a passage extending from the cylinder head to a thermostat via the radiator, the (b) passage for the heater core a passage extending from the cylinder head to return to the cooling water pump via the room heating heater core. The (c) passage for the oil cooler is a passage extending from the cooling water pump to return to the same via the oil cooler, and the (d) bypass passage a passage extending from the cylinder head and shunting these units to directly reach the thermostat.
The (a) passage for the radiator, which passes the radiator, is provided to prevent the engine from being overheated, by cooling the cooling water which has cooled the cylinder block and cylinder head of the engine, and which has been increased in temperature due to the heat exchange.
The (b) bypass passage shunting the radiator is provided to prevent the cooling water from being over-cooled, since the excessive cooling of the cooling water at the time of starting the engine and at a cold time causes not only the deterioration of an engine output and fuel efficiency of the engine but also bad influence upon the engine, such as low-temperature abrasion of cylinders.
In order for the temperature of the cooling water to stay within a proper temperature range, the switching of the (a) passage for the radiator and (d) bypass passage is controlled. This switching control operation is carried out by opening either one of these passages by utilizing the expansion and contraction of a wax-packed temperature sensing member, which occur due to the temperature of the cooling water flowing in the temperature sensing member, in for example, a two-valve type thermostat wherein the passage for the radiator is joined to one inlet thereof with the bypass shunting the radiator joined to the other inlet thereof.
Namely, when the temperature of the cooling water becomes high, the (a) passage for the radiator is opened, and the (d) bypass passage shunting the radiator is closed. Conversely, when the temperature of the cooling water becomes low, the (a) passage for the radiator is closed, and the (d) bypass passage shunting the radiator is opened.
The cooling water circulating structure is also provided with the (b) passage for the heater core for the purpose of circulating the cooling water, which has cooled the engine body, and which has thereby been heated, to the heater core which is used to heat the room.
The (c) passage for the oil cooler, which is adapted to supply cooling water to the oil cooler, is provided so as to cool a lubricating oil for the engine.
In a relative art cooling water circulating structure, the four-system cooling circulating passage comprising the (a) passage for the radiator, (b) passage for the heater core, (c) passage for the oil cooler, and (d) bypass passage and a lubricating oil circulating passage are required. Since the pipes forming these passages are arranged in a mixed state around the engine body as they are kept away from projections of devices, a large number of pipes, a large piping space and a large space for carrying out piping work become necessary, so that the miniaturization of the engine is hampered.
Since a large number of pipes are arranged in a complicated manner in a small space, they obstruct a movement of a tool during the fixing of devices, the removing thereof and the inspecting thereof. This causes an assembling operation to become troublesome, and also the work efficiency in the inspection and maintenance work to lower.
In view of these problems, one of the applicants of the present invention proposed a structure of a thermostat housing for internal combustion engines by Japanese Patent Laid-Open No. 13935/1997. This thermostat housing has a structure in which an oil cooler and an oil filter are fixed so that they are unitary with each other with some of the external pipes replaced with pipes in the thermostat housing. This enables a piping space to be saved, and the efficiency in the part fixing and maintenance work to be improved.
Concretely speaking, a cooling water circulating structure using the thermostat housing of this construction is provided with an oil cooler 7' under the thermostat housing 10', and an oil filter 8' of a laminated construction under the oil cooler 7' as schematically shown in the construction diagram of a circulating system of FIG. 11 and the explanatory perspective view of FIG. 12, so that the oil filter 8' projects downward.
This causes the space occupied by parts around the engine to increase. Consequently, in a certain type of engine, the oil filter interferes with auxiliary devices, and the space occupied by parts around the engine becomes excessively large, so that it becomes difficult to provide the oil filter in an engine room.
Moreover, when the oil cooler 7' only in this apparatus is inspected or replaced, the oil filter 8' fixed to the lower side thereof has also to be removed at the same time. Therefore, the work efficiency lowers.
In a relative art cooling water circulating structure shown in FIGS. 11 and 12, a passage H for a heater core which passes the heater core 6 and a passage C for an oil cooler which passes the oil cooler 7' are independent of each other, and these two passages meet each other in the interior of a thermostat housing 10' to extend toward the downstream side of a thermostat 9.
Accordingly, a passage between a cooling water pump 11 and cooler 7, and a pipe between the oil cooler 7' and thermostat 9 become necessary, i.e., a large number of pipes are still required.
Moreover, the detection of the temperature of the cooling water, which is necessary for the controlling of the switching of a passage R for a radiator and a bypass passage B, is carried out by a temperature sensing member 9a of the two-valve type thermostat 9 as shown in FIG. 11. This temperature sensing member 9a is provided in a portion in which one inlet port to which the passage R for the radiator is joined and the other inlet port to which the bypass passage B is joined communicate with each other, and this portion faces a discharge port.
Either one of the passage R for the radiator and bypass passage B is opened depending upon the temperature of the cooling water around the temperature sensing member 9a, and the cooling water is supplied from the discharge port to a cooling pump 11. A flow rate of the cooling water from the radiator is controlled in accordance with the use of these passages, whereby the temperature of the cooling water is regulated so that it stays in a predetermined range.
According to this control method, when the thermostat 9 opens the passage R for the radiator, the cooling water which has passed through the radiator 5 and decreased in temperature flows onto the temperature sensing member 9a, so that the temperature sensing member 9a is rapidly cooled with this low-temperature cooling water. Therefore, in the case where a wax type thermostat 9 is used, the wax in the temperature sensing member 9 contracts, and, consequently, the bypass passage B is selected and opened.
At the very moment the bypass passage B is opened, the high-temperature cooling water which is not cooled, and which returns directly from a cylinder head 2, flows onto the temperature sensing member 9a. Consequently, the temperature sensing member 9a is heated rapidly and expands to cause the passage R for the radiator to be opened again. These actions are necessarily repeated in a complicated manner, so that hunting occurs. The hunting occurs because the passages are controlled by the high-temperature cooling water and low-temperature cooling water a difference in temperature of which is large.
An ecofilter a demand for the use of which has increased greatly in recent years uses a container as it is so that a filter element 8' only can be replaced. When this ecofilter is used, it is necessary that a case for a cartridge be divided into two for the replacement of the filter element 8a'. Therefore, the number of portions to be joined together and that of parts increase correspondingly, so that the efficiency in assembling and inspection operations lowers.